[TIP] mock.patch in version 0.5 doesn't mock __exit__ method on open files
fuzzyman at voidspace.org.uk
Mon Jul 13 04:11:11 PDT 2009
Technically this is a bug in Python (which will be fixed in 2.7 / 3.2)
where __enter__ / __exit__ are looked up on the instance rather than the
That doesn't help you however. :-)
Not sure why this works in 0.4 and fails in 0.5 - it shouldn't have
worked in 0.4 either. Mocking magic methods (awesome alliteration) is a
tricky one as it will need custom support in Mock. In general I don't
think the magic methods should exist on mock objects unless the
programmer has configured them, so I need a simple way for the user of
mock to specify which magic methods should exist.
Mock is due for an update so I will think about this. I'll work out a
suggested API for your feedback. I guess you want __enter__ to return a
mock object that you can track and __exit__ to record calls to and
return a boolean.
All the best,
Matthew Wilson wrote:
> This test passes when I use mock 0.4 and fails with 0.5:
> def test_to_html(o):
> global b
> b.to_html('bogus filepath')
> Here's the definition of b.to_html:
> def to_html(self, filepath):
> Write this bag out as HTML to a file at filepath.
> with open(filepath, 'w') as f:
> mock 0.5 has this code:
> 128 def __getattr__(self, name):
> 129 if self._methods is not None:
> 130 if name not in self._methods:
> 131 raise AttributeError("Mock object has no
> attribute '%s'" % name)
> 132 elif _is_magic(name):
> --> 133 raise AttributeError(name)
> When __exit__ gets called, that code raises the AttributError.
> I can see good reasons fo not mocking magic methods automatically, but
> can I explicitly say I do want __open__ and __exit__ to be mocked?
> mock is great software by the way.
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